Bed sheets that are applied to mattresses typically include a bottom sheet and a top sheet. While the bottom sheet might be a "fitted" sheet in that it is formed to surround the sides and ends of the mattress as described in my U.S. Pat. No. 4,773,341, the top sheet typically is flat, having folded hems formed at the foot and head of the sheet, and selvage at the side edges of the sheet. During the production of the flat sheets, a long length of the sheet material must be handled during the hem folding and sewing function. While a static folder can be employed to form such long and typically wide folds of the sheet material, the longer the sheet material and the more flimsy the sheet material, the more difficult it is to accurately control the fold. One of the more expensive aspects of the fabrication of sheets is the manual handling of the bed sheet as it is sewn by the operator through a sewing machine. The operator must manipulate the large segments of sheet material when performing the sewing functions. Therefore, it is highly desirable to perform the turning and sewing of hems in a continuous and automated system, if possible.